Add support for EMS heatpump water heaters.

Issue #751

ACKNOWLEDGEMENTS.md

@@ -343,3 +343,4 @@ Further device support has been made with the assistance of users.  Please consi
 - [Batav93](https://github.com/Batav93) for assisting with support for Duux Whisper Flex fans.
 - [Atirion](https://github.com/Atirion) for assisting with support for Nedis Door/Window sensors.
 - [allanak](https://github.com/allanak) for assisting with support for Ovlaim ceiling fans.
+- [nk00li](https://github.com/nk00li) for assisting with support for EMS hot water systems.

DEVICES.md

@@ -75,6 +75,7 @@
 ### Water heaters
 
 - Aquatech Rapid/X6 heat pump water heaters
+- EMS Thermal 200L domestic heat pump hot water system
 - Hydrotherm Dynamic/X8 heat pump hot water systems
 - ITS-4.5HD super water heatpump
 - Thermex IF series V pro hot water systems

custom_components/tuya_local/devices/ems_waterheater.yaml

@@ -0,0 +1,57 @@
+name: Water heater
+products:
+  - id: nqlqesmkrje7vdhm
+    name: EMS Thermal TH200DT heatpump
+primary_entity:
+  entity: water_heater
+  dps:
+    - id: 1
+      type: boolean
+      name: operation_mode
+      mapping:
+        - dps_val: false
+          value: "off"
+        - dps_val: true
+          constraint: mode
+          conditions:
+            - dps_val: auto
+              value: heat_pump
+            - dps_val: mix
+              value: high_demand
+            - dps_val: electric
+              value: electric
+    - id: 2
+      type: integer
+      name: temperature
+      range:
+        min: 10
+        max: 70
+      unit: C
+    - id: 4
+      type: string
+      name: mode
+      hidden: true
+    - id: 9
+      type: bitfield
+      name: fault_code
+secondary_entities:
+  - entity: sensor
+    class: temperature
+    dps:
+      - id: 3
+        type: integer
+        name: sensor
+        unit: C
+        class: measurement
+  - entity: binary_sensor
+    name: Fault
+    class: problem
+    category: diagnostic
+    dps:
+      - id: 9
+        type: bitfield
+        name: sensor
+        mapping:
+          - dps_val: 0
+            value: false
+          - value: true